Analytical model for saturable aging in semiconductor lasers

We present an expression for the change in threshold current of a semiconductor laser diode as a function of the aging time under constant thermal and current aging. The expression forms a sigmoidal shape with the aging time, and is accurate in describing the increase of threshold current during aging. In the case where nonlinearities or “knees” occur in the threshold current aging curve, a multicomponent defect model is utilized to explain the observation. This multicomponent defect model allows multiple sigmoidal curves to be incorporated into the description. Each sigmoidal curve is thought to represent the growth of one type of defect complex. The parameters in the model are designed to have physical meaning that corresponds to the properties of the laser material. The model is compared to five popular models used to describe the threshold current aging characteristics.